Quarterly report on the strontium heat source development program, advanced systems and materials production division for July-September 1978.

Abstract

Metallographic examination of the specimens from the 12,000-hr tests with /sup 90/SrF/sub 2/ was completed this quarter. The 12,000-hr Hastelloy C-276 specimens exhibited substantially greater attack than did the 6000-hr specimens. The 12,000-hr Haynes 25 and TZM specimens, however, showed no more attack than did the 6000-hr specimens. The 20,000-hr tests with /sup 90/SrF/sub 2/ have also been completed, and arrangements have been made to ship the capsules to Oak Ridge National Laboratory (ORNL) for examination. Hydrostatic pressure testing of the AISI-1018 steel prototype outer capsules was completed. The 0.4-in. wall capsule collapsed at 11,200 psi, while the 0.5-in. wall capsule collapsed at 15,900 psi. THe 0.6-in. wall capsule did not collapse at the maximum test pressure of 20,000 psi, but did exhibit slight ovality after testing. The capsules were subjected to a helium leak check and no leaks were detected. Additional evaluation and destructive examination of the capsules are now underway. The 5000-hr oxidation tests with Hastelloy S and Hastelloy C-4 were completed. At 600/sup 0/C oxidation of both alloys continued to adhere to parabolic rate relationships. At 700/sup 0/ and 800/sup 0/C, however, oxidation of the two alloys after 5000-hr exposure was less than predicted by the parabolic rate equations that fitted the shorter-term data. Testing of the tensile specimens from the 1000- and 2500-hr oxidation tests indicates that oxidation of the two alloys at 600/sup 0/ to 800/sup 0/C has no significant effect on their room-temperature tensile properties.